to remove oxygen from a compound, or cause to react with hydrogen or form a hydride, or to undergo an increase in the number of electrons1

make smaller1

reduce an image1

reduce in size; reduce physically1

make less complex1

reduce a problem to a single question1

reduce in scope while retaining essential elements1

cut down on; make a reduction in1

reduce your daily fat intake1

destress and thus weaken a sound when pronouncing it1

reposition (a broken bone after surgery) back to its normal site1

undergo meiosis1

The cells reduce1

lower in grade or rank or force somebody into an undignified situation1

She reduced her niece to a servant1

simplify the form of a mathematical equation of expression by substituting one term for another1

lessen and make more modest1

reduce one's standard of living1

bring to humbler or weaker state or condition1

He reduced the population to slavery1

put down by force or intimidation1

In a graphical user interface, to decrease the size of a window. A user can reduce a window either by clicking the appropriate button in the title bar or by clicking the mouse on the border of the window and dragging the border toward the middle of the window.2